Four on Green Line / Green Lights

Updated 9/18/2014 with MPR article

Fred Melo writes in the Pioneer Press about Always Green Traffic Control “Green Line: Inventor proposes using timing, speed to improve travel time

“Ultimately, the decision whether or not to implement a system such as this along the Green Line would need to be made by Metro Transit’s project team,” said Kari Spreeman, a spokeswoman with the St. Paul Department of Public Works.

David Levinson, an engineering professor at the University of Minnesota who specializes in transportation issues, has blogged about “Always Green” on his website,

“It’s an interesting idea,” Levinson said. “Even if the total travel time is the same in both cases, it’d be better than going fast and then stopping. You might even save some time. After you stop, you have an acceleration-deceleration loss (in travel time).”

Levinson acknowledged one drawback, however. “It’s never been tested,” he said.

Tim Harlow at the Star Tribune writes in his column The Drive: Nick Musachio and the Always Green Traffic Control

David Levinson, a transportation expert at the University of Minnesota, says the Always Green Traffic Control has potential.

“I think it would work best for isolated intersections on rural expressways, but there is no reason it couldn’t work in an urban area,” Levinson said. “Static speed signs have been used for decades on Connecticut Avenue in Washington, D.C. Something dynamic should do even better. I do believe it warrants a field test.”

Musachio faces the challenge of getting somebody to do just that. He’s been bending ears of the St. Paul Public Works Department, but so far they have not bitten.

“In theory the system could work, but it has not been tested in a real environment. Until that happens, we won’t consider it,” said city spokeswoman Kari Spreeman.

Marion Renault at MPR writes “Inventor says synchronized lights could boost Green Line travel time” [I hope by “boost” she means reduce.]

“You can either change the lights to match the vehicles,” said David Levinson, a civil engineering professor at the University of Minnesota. “Or you can change the vehicles to match the lights.”

Levinson said keeping cars moving at a steady speed is optimal for traffic flow. But he said it takes a lot of coordination and a tightly-maintained fixed traffic system to create a grid of alternating, forward-moving platoons of cars and trains.

Jessie Bekker at MnDaily writes “Signs could speed up Green Line
The signs would suggest speeds to help drivers and light rail conductors make green lights on time and increase efficiency.

Though Musachio is certain the system would work “perfectly” with the Green Line, David Levinson, associate professor [sic] in the Department of Civil Engineering [double sic], isn’t so sure.

“The Green Line is all tied up in politics,” he said.

Levinson said the system warrants a field test but believes a rural or suburban traffic signal is the place to start before it moves to an urban area.

Previously here and here and here.

2 thoughts on “Four on Green Line / Green Lights

  1. so what advantage does this untested technology have over well established green signal attenuation for public transit.emergency vehicles via microwave/fiberoptic systems?


  2. The advantage of this technology over transit pre-emptive systems is that this technology doesn’t interfere with vehicular cross traffic. Thus it doesn’t add to congestion. The proposed light rail application of this technology is on a corridor where the trains pass over 50 signalized cross streets, Preemption would therefore interfere with over 200,000 cross-traffic vehicles, thus exacerbating, an already congested corridor.

    Additionally, the technology is not just for transit vehicles; it is a revolutionary treatment of intersection control called kinetic intersection control, controlling an intersection while keeping all traffic streams in motion. To accomplish this, vehicles are controlled about 25-40 seconds upstream of the intersection by means of a variable speed limit display, which gives 100% of all drivers precise speed information. Obeying this information is in the driver’s self interest if they wish to make a green light. If the driver’s aren’t going to make the green light they are simply given the fastest lower speed at which they are guaranteed to make a green light.

    By following the speed recommendation, platoons form which arrive at given intersections just after lights turn green. By keeping all vehicles in motion, queueing is avoided, wasted green is avoided, emissions are radically cut, and intersections can handle much more volume thus reducing congestion and wasted green time.

    True the technology hasn’t been field tested, but calling the technology untested is a somewhat misleading since modeling of the technology on sophisticated Aimsun software proves it out in dramatic fashion, handling 7100 total vehicles per hour through an intersection with no queueing whatsoever in any direction. The corresponding traditionally controlled intersection had rolling multi cycle queues in all directions. Additionally, deployment it is not totally unprecedented in that it is related to, and improves upon established Green Wave technology that has been successfully deployed worldwide, especially in the Netherlands.

    There are certainly no technological barriers, nor theoretical barriers to implementing it. Basically it boils down to driver compliance, and there it only depends upon the first, leading edge drivers of the traffic stream complying. After that, following vehicles have little choice but compliance, since leading edge drivers form a speed barrier; and thusly, are formed dense, controlled velocity, platoons that arrive at intersections, usually at 2/3 of the speed limit, and shortly after the lights turn green. If this sounds complicated, just watch the modeling videos and it makes it will quickly make more sense.

    Nick Musachio
    Inventor of Always Green Traffic Control, a kinetic intersection control technology.
    I can be contacted at musachio at


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